A heterogeneous "resting" pool of synaptic vesicles that is dynamically interchanged across boutons in mammalian CNS synapses.
Using pHluorin-tagged synaptic vesicle proteins we have examined the partitioning of these probes into recycling and nonrecycling pools at hippocampal nerve terminals in cell culture. Our studies show that for three of the major synaptic vesicle components, vGlut-1, VAMP-2, and Synaptotagmin I, approximately 50-60% of the tagged protein appears in a recycling pool that responds readily to sustained action potential stimulation by mobilizing and fusing with the plasma membrane, while the remainder is targeted to a nonrecycling, acidic compartment. The fraction of recycling and nonrecycling (or resting) pools varied significantly across boutons within an individual axon, from 100% resting (silent) to 100% recycling. Single-bouton bleaching studies show that recycling and resting pools are dynamic and exchange between synaptic boutons. The quantitative parameters that can be extracted with the approaches outlined here should help elucidate the potential functional role of the resting vesicle pool.
Fernandez-Alfonso
Tomas
T
Department of Biochemistry, Weill Medical College of Cornell University, 1300 York Ave, New York, NY 10021, USA.
Ryan
Timothy A
TA
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D004558:Electric Stimulation / Q000379:methods; D004594:Electrophysiology / Q000379:methods; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology; D008561:Membrane Fusion / Q000502:physiology; D018613:Microscopy, Confocal / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D009474:Neurons / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D017729:Presynaptic Terminals / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000378:metabolism / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D013572:Synaptic Vesicles / Q000378:metabolism / Q000502:physiology; D050863:Synaptotagmin I / Q000235:genetics / Q000378:metabolism; D050988:Vesicle-Associated Membrane Protein 2 / Q000235:genetics / Q000378:metabolism; D050598:Vesicular Glutamate Transport Protein 1 / Q000235:genetics / Q000378:metabolism
C485187:PHluorin; C493466:Slc17a7 protein, rat; D050863:Synaptotagmin I; D050988:Vesicle-Associated Membrane Protein 2; D050598:Vesicular Glutamate Transport Protein 1; D049452:Green Fluorescent Proteins